You guys are killing me. Everyone, buy a PC12 and fly it and then compare.

Compare to what? A Duke? HAHA

No, my point is that there is a lot of opinion about how to run your plane and nobody here has one. As far as I am concerned you can run it 150% n1 and I could care less. If you get there safely and can afford the gas bill who really cares?

We ran our U5 Unlimited hydro at 145% (107% officially to the black box) and it did just fine. I think we were turning about 80% more torque than the old T-58 Lycoming was rated to produce and that was done on water taking on 2' chop pounding the crap out of the boat.

As for Dukes, yeah they are an old whore, but who really cares? It got my family from IN to FL in comfort at 25k ft in 4 hours. Would have been 3:20 in the 12NG for about $2.3M more money. When I want a *real* airplane I stroke a check to ride in the Hawker when I really need to. The Phenothing is a toy compared to a real jet and the Pilatus is like a Tomahawk compared to the Hawker.

"Couldn't" care less.

It's all about lift, thrust, weight and drag. If you can't first explain your theory in the context of these simple forces, going into further detail is fruitless.

Let us set up a simple thought experiment for discussion so that we can properly bracket the problem.

Say we have a flight test department. We have a pc12, complete with its 1200 shp engine and standard 4 blade prop. Say we also have a couple of pc12s that we have modified. We have done an amazing modification in that we've put two engines on them, one in a traditional manner, the other combined that works through a single shaft.

So these are, remarkably, all very similar aircraft. #1 is un modified, 2 is a standard twin and 3 is a two engine one prop arrangement.

Imagine that on the engines, we have made another modification such that when we throw a switch in the cockpit, a little chamber or valve or widget inside the engine opens up, allowing the engine to now deliver 1 extra horsepower to the shaft. Don't worry how, just accept that it produces exactly one unit of extra power.

Now we go fly, side by side, same conditions and imagine we set up the engine on the single such that it is producing full rated power of 1200 shp. We set the prop to a constant rpm and do not change it. Now we flip the switch and suddenly we are producing 1201shp. The engine is delivering more torque to the prop, it does not spin any faster because the prop controls itself, but that extra power produces incrementally more thrust. Call it x pounds. Don't worry what this does to airspeed. Don't worry what this does to fuel flow. Don't worry about efficiency. Just worry about one thing: Thrust. Thrust is now greater. x pounds greater to be exact. Remember, thrust is the force acting to move the airplane forward.

In the traditional twin we do the same thing. Same props, same conditions. We throw the switches. Now we produce 1201 and 1201. Thrust increases. It goes up x for engine number one and x for number two, just the same way it did in aircraft 1. Again, don't worry how that translates into airspeed or fuel flow or anything else at this point. Don't worry about extra drag or extra lift. The force that moves the aircraft forward increases by x + x. That equals 2x.

The crew in the third aircraft now throws the switches in their pc12 with the 2 engines working on a single shaft. Power again increases to the shaft. The prop spins no faster. Power goes up through increased torque, same as before. Thrust, again, increases by 2x.

Jason's claim, which I reject, is that somehow flipping the switches in aircraft #3 produces something greater than 2x thrust. Or throwing the switches in aircraft #2 produces something less than 2x thrust.

Todd - with great respect, your experience with the Duke cannot be taken seriously - it is based on ownership of a couple of cheap planes which you owned less than 50 hours and took on a handful of short family trips, and which left you stranded in between catch-up maintenance that you complained about incessantly on BT. If you would have owned either of those Dukes for more than 200 or 300 hours, they would have eaten your lunch and you would have spent a fortune trying to keep them flying.

A Pilatus has a high purchase price but you get what you pay for. It is extraordinarily capable and has the lowest cost per mile in its class. A PC-12 is a true business tool - an 80K Duke cannot be taken seriously as a mode of transportation that you need to rely on. Cheap Dukes are unreliable and cannot be used for business purposes - if you have time to spare - then they might be ok.

So "drag" is the only factor?

Why didn't you respond like this in the first place instead of being ...[admin edit]

lol

You mean "You haven't discussed drag". It's been discussed as much as 2 v 1. You're just not reading the thread.

I meant in my little thought experiment.

Todd is the youngest, old guy on BT.

Remember this Jason? It was yesterday.

Perhaps you remember typing this several hours ago.

Jason is just going off of a basic observation, which "everyone knows":

A Baron with two engines, each making 300hp, burns twice as much fuel as a Bonanza with one, but it is nowhere close to twice as fast.

Thrust is additive, and therefore the twin does, in fact, produce twice the thrust. So why isn't it much faster than the single?

One can oversimplify the situation a bit and still get a clear picture as to why this phenomenon holds for pistons, turboprops, and jets.

1) Drag increases relative to the square of speed. Therefore, the Baron doing 190 KTAS is producing significantly more drag than the Bonanza doing 170 KTAS.
2) The added weight and (especially) drag of the second engine slow the twin down.

That's all there is to it. The extra thrust provided by the second engine results in a little more speed, but much of it is wasted on drag. Note that climb performance generally exhibits a much larger difference between the single and the twin, because drag is much lower at the climb airspeeds.

Do you understand how forums work? It's a flow of information. It's the back and forth that leads to final outcome.

I made it very clear that I don't design aircraft for a living. Along with the post you just quoted are 10 other posts of me asking questions and throwing out ideas.

For you to take the position you took is foolish. At no time did I say "I'm an engineer, I do this for a living and this is the answer. You're taking my post out of context. Go quote the rest of the stuff I wrote. Better yet, why don't you go read it... for the first time.

In my opinion, still nobody has come in here and answered the question beyond a shadow of a doubt. As of now, the only difference between a single and a twin of equal horsepower is drag. If that's the case, so be it. I'm not sure I'm buying it but I DON'T KNOW. If I did I wouldn't be discussing it.

Hell Tyler, at least I discuss new stuff around here. [admin edit]